Setting Up a Standby Database An existing database can be configured to have a standby database. The first step is to install the Oracle software on the standby server. The database already exists on the primary server. The primary database will need some configuration with standby logs and parameters. Connections to the secondary database can be set up, and then using RMAN, the initial copy of the database can be set up on the standby server. On the primary database, the following needs to be done: SQLPLUS> alter database force logging; Database altered. ## Create the standby log files. They need to be the ## same size or larger than the primary database SQLPLUS> alter database add standby logfile '/u01/oracle/db01/stby01.log' size 50M; Database altered. SQLPLUS> alter database add standby logfile '/u01/oracle/db01/stby02.log' size 50M; Database altered. ## Continue creating the log files. One more log group ## than on the primary is recommended ## Parameters SQLPLUS> show parameter db_name NAME TYPE VALUE db_name string DB01 ## Name stays the same SQLPLUS> show parameter db_unique_name NAME TYPE VALUE db_unique_name string DB01 ## Standby and Primary will need unique names ## Names do not change even if roles switch SQLPLUS> alter system set LOG_ARCHIVE_CONFIG='DG_CONFIG=(db01,dbstby01)' System altered. SQLPLUS> alter system set log_archive_dest_2= 'service=dbstby01 async valid_for=(online_logfile, primary_role) db_unique_name=dbstby01'; 292 Oracle Database Administration for Microsoft SQL Server DBAs System altered. ## The standby database server should already have the ## software and the needed directories for the database ## Create a parameter file for the standby with just the DB_NAME > cat initdbstby01.ora DB_NAME=dbstby01 > export ORACLE_SID=dbstby01 SQLPLUS> startup nomount pfile=$ORACLE_HOME/dbs/initdbstby01.ora ORACLE instance started. SQLPLUS> exit ## To primary database run RMAN to copy database RMAN> connect target connected to target database: DB01 (DBID=1382128337) RMAN> connect auxiliary sysdbstby01 connected to auxiliary database: DBSTBY01 (not mounted) RMAN> run { allocate channel disk1 type disk; allocate auxiliary channel disk2 type disk; duplicate target database for standby from active database spfile parameter_value_convert 'db01','dbstby01' set db_unique_name='dbstby01' set db_file_name_convert='/db01/','/dbstby01/' set control_files='/u01/oracle/oradata/dbstby01.ctl' set fal_client='dbstby01' set fal_server='db01' set standby_file_management='AUTO' set log_archive_config='dg_config=(db01,dbstby01)' set log_archive_dest_1='service=db01 ASYNC valid_for= (ONLINE_LOGFILE,PRIMARY_ROLE) db_unique_name=db01'; } ## Can test the standby by switching the log file on the primary > export ORACLE_SID=DB01 SQLPLUS> alter system switch logfile; System altered. In summary, the basic steps are as follows: 1. Install the software on the standby server. 2. Configure the parameters on the primary server. 3. Make the connections by updating tnsnames.ora and listener. 4. Use RMAN to copy the database. Chapter 10: High-Availability Architecture 293 SQL Server has a manual process for the management of failover for log shipping. The Oracle Data Guard failover can be configured to occur automatically. You can use the Data Guard broker and management tools to set up the automatic failover and manage the standby servers. The Data Guard broker needs to be running on both the primary and standby server. A listener entry for the Data Guard broker on the primary and standby servers will help with failover and avoiding TNS errors. ## Parameter for starting the broker SQLPLUS> alter system set DG_BROKER_START=TRUE scope=both; System altered. ## Example listener entry (SID_LIST = (SID_DESC = (GLOBAL_DBNAME = db01_dgmgrl) (ORACLE_HOME = /u01/oracle/11.2.0/db_1) (SID_NAME = db01) ) ) Using the Data Guard broker is similar to starting SQL*Plus from the command line. Enter dgmgrl to start the utility and then issue commands. ## Create a broker configuration > dgmgrl DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production Copyright (c) 2000, 2009, Oracle. All rights reserved. Welcome to DGMGRL, type "help" for information. DGMGRL> create configuration 'DG_DB01' AS PRIMARY DATABASE is 'db01' CONNECT IDENTIFIER is 'db01'; Configuration "DG_DB01" created with primary database "db01" DGMGRL> add database 'dbstby01' AS CONNECT IDENTIFIER is 'dbstby01'; Database "dbstby01" added. DGMGRL> enable configuration Enabled. DGMGRL> show configuration 294 Oracle Database Administration for Microsoft SQL Server DBAs Configuration Name: DG_DB01 Enabled: YES Protection Mode: MaxAvailability Databases: db01 – Primary database dbstby01 – Physical standby database Fast-Start Failover: DISABLED Current status for "DG_DB01': SUCCESS Other utility commands can be used to do a switchover, which changes the roles of the servers between primary and standby, or failover, which will fail the primary over to the standby database. The default configuration for Fast-Start Failover is disabled. When it is enabled, it can use triggering events to implement the failover to the standby server. Events include connection loss, instance crash, a shutdown abort on the primary, and different database health checks such as loss of a datafile. With these events, you can set thresholds to have more control over when the failover occurs. This lets you avoid situations where a small hiccup in the connection or a busy server that doesn’t allow a quick check will cause the system to failover. The Data Guard configurations can be modified to automate the failover for certain thresholds. If there is more than one standby database, the FastStartFailoverTarget property should be set so that the primary and standby database reference each other. DGMGRL> edit database DB01 set property FastStartFailoverTarget = 'dbstby01'; DGMGRL> edit database DBSTBY01 set property FastStartFailoverTarget = 'db01'; DGMGRL> edit configuration set property FastStartFailoverThreshold = '180'; NOTE With automatic failover, the DBA can be assured of continuing service without having to log in. However, the DBA may need to be concerned about unnecessary failovers. Chapter 10: High-Availability Architecture 295 Maximum Availability Architecture includes a combination of these solutions, as shown in Figure 10-5. The Oracle RAC database can be a primary and a standby server. When the Maximum Protection option is chosen for the Data Guard configuration, having RAC set up on the standby database will reduce the risk for the logs to be applied. Figure 10-5 shows the architecture of the Oracle RAC database with the Data Guard standby database. 296 Oracle Database Administration for Microsoft SQL Server DBAs Interconnect RAC production database primary site Interconnect RAC standby database secondary site Oracle Data Guard Dedicated network FIGURE 10-5. Oracle Maximum Availability Architecture ASM in an RAC Environment We have discussed how it is useful to have the ASM instance available for the disks of the database, but have not yet looked into the details about how to manage the instance. In the Oracle RAC environment, there needs to be an ASM instance for every node in the cluster, but one ASM instance can support multiple instances on that node. Managing ASM Disk Groups The ASM disk groups serve as containers for consolidating databases and file systems to be able to use the storage more efficiently and even share between databases. The ASM Configuration Assistant (ASMCA) helps you create and manage disk groups. As shown in Figure 10-6, new disks can be added to the disk group here, and attributes of the disk group can be edited. Other ASMCA options allow you to manage the volumes and file system in a clustered environment. Chapter 10: High-Availability Architecture 297 FIGURE 10-6. Using ASMCA ASMLib is the support library for ASM. It is used for initialize the disk for usage with ASM. The Linux package for the ASMLib needs to be installed for usage. >rpm -Uvh oracleasm-2.6.18-8.el5-2.0.4-1.el5.i686.rpm \ oracleasm-support-2.0.4-1.el5.i386.rpm \ oracleasmlib-2.0.3-1.el5.i386.rpm ## Configure ASMLib >/etc/init.d/oracleasm configure Configuring the Oracle ASM library driver. ## Create disks >/etc/init.d/oracleasm createdisk ORADATA01 /dev/sda1 Marking disk "/dev/sda1" as an ASM disk: ## To see the disks that were created >/etc/init.d/oracleasm listdisks ORADATA01 ORADATA02 ORADATA03 ORADATA04 298 Oracle Database Administration for Microsoft SQL Server DBAs ASM Configuration Parameters The ASM instance is really a process and a bit of memory. Some parameters go into the spfile for configuration of this instance. These parameters provide the details about the type of instance and where the disks are located for creating the disk groups. ■ INSTANCE_TYPE Set to ASM (default is RDBMS) ■ ASM_DISKGROUPS Lists the disk groups that should be mounted ■ ASM_DISKSTRING A value that indicates where to discover the disks that are available to add to a disk group ■ ASM_POWER_LIMIT Maximum power for rebalancing operation, a value between 1 and 11 (higher number for faster rebalancing) The information stored in the ASM instance is the metadata about the disks, disk groups, names, and directories. The Oracle database creates the data in the files when the disk groups are allocated to a database. The ASMCMD command-line utility can help you manage the files. It provides a quick way to find out information about what the ASM instance is managing and where the database files are located. You can take backups, make copies, and move files. ASMCMD commands are similar to file commands in a Linux environment. Here are some examples of using ASMCMD: >asmcmd ASMCMD> ls –l State Type Rebal Name MOUNTED NORMAL N DG_DATA01/ MOUNTED NORMAL N DG_DATA02/ ASMCMD> cd DG_DATA01 ASMCMD> ls –l Type Redund Striped Time Sys Name Y ASM/ Y DADEV/ Y DSDEV/ Y SQLTEST/ ASMCMD> cd DADEV ASMCMD> ls –l Type Redund Striped Time Sys Name Y DATAFILE/ Y PARAMETERFILE/ Y TEMPFILE/ N spfileDADEV.ora => +DG_DATA01/DADEV/PARAMETERFILE/spfile.269.714035663 ## Search for the spfile ASMCMD> find / spfile* +DG_DATA01/DADEV/PARAMETERFILE/spfile.269.714035663 +DG_DATA01/DADEV/spfileDADEV.ora ## Check SPACE ASMCMD> du Used_MB Mirror_used_MB 23798 47605 ## Back up a disk group ASMCMD> md_backup /bkup/dg1_backup –G 'DG_DATA01' ## The –G parameter is optional; if none chosen, it will ## back up all of the disk groups ## See all connected instances ASMCMD> lsct Chapter 10: High-Availability Architecture 299 ASMCMD> lsct DB_Name Status Compatible_version Instance_Name Disk_Group +ASM CONNECTED 11.2.0.1.0 +ASM DG_DATA01 DADEV CONNECTED 11.2.0.1.0 DADEV DG_DATA02 DBDEV CONNECTED 11.2.0.1.0 DBDEV DG_DATA02 SQLTEST CONNECTED 11.2.0.1.0 SQLTEST DG_DATA01 These simple commands demonstrate the following: ■ Find out how much space is available on one of the disk groups ■ Find out which instances are connected to which disk groups ■ Find a file ■ Execute a backup of one disk group With ASM, even though everything is laid out in the directories of the disk groups, creating tablespaces is very simple. You just use a CREATE TABLE statement with a disk group and a size. >export ORACLE_SID=DADEV >sqlplus SQLPLUS> create tablespace USER_DATA datafile '+DG_DATA01' size 2048M; Tablespace created. Then you have disk space available for users to start filling up with their tables, objects, and whatever data they need to store. As you have come to expect, OEM also offers a way to manage the ASM disk groups and files. Figure 10-7 shows the OEM display of the disk groups of the ASM instance. In OEM, the ASM instance is available from any of the database instances that are using the ASM instance. You can mount the disk groups through this OEM view. You can see information about the disks, including the status, the type of redundancy that the disk is configured for, and the space that is allocated and used. You can also do some health checks and rebalance the disks. Selecting one of the disk groups will drill down into a view of the files on the disks, as shown in Figure 10-8. If you find it difficult to work with the file names with all of those numbers, you can create an alias or rename files. 300 Oracle Database Administration for Microsoft SQL Server DBAs Chapter 10: High-Availability Architecture 301 FIGURE 10-7. OEM view of ASM disk groups FIGURE 10-8. OEM view of files in a disk group . risk for the logs to be applied. Figure 10-5 shows the architecture of the Oracle RAC database with the Data Guard standby database. 296 Oracle Database Administration for Microsoft SQL Server DBAs Interconnect RAC. 'dbstby01'; Database "dbstby01" added. DGMGRL> enable configuration Enabled. DGMGRL> show configuration 294 Oracle Database Administration for Microsoft SQL Server DBAs Configuration Name:. disks that were created >/etc/init.d/oracleasm listdisks ORADATA01 ORADATA02 ORADATA03 ORADATA04 298 Oracle Database Administration for Microsoft SQL Server DBAs ASM Configuration Parameters The